This experiment was carried out to study the relationship between hete
rosis and the polymorphism of genetic markers in rice. We employed 14
varieties, 4 japonica, 4 javanica and 6 indica. Of all the 91 possible
combination, one indica X indica cross was missing, so 90 F1 cross co
mbinations were used for half diallel analysis. They were transplanted
in a field at 40 x 60 cm spacing and the top part of the plants was s
ampled and dried 43 days after transplanting to examine the degree of
heterosis of biomass. The diallel analysis of the heterosis of biomass
showed that dominant effect was larger than additive effect, suggesti
ng that heterosis was contributed by the accumulation of dominant gene
s. More than 10 genes were considered to be involved in the heterosis.
The general combining ability of biomass was highly significant and t
he heterosis of hybrids from crosses between indica and japonica varie
ties were generally large. Significant relationships were observed bet
ween the heterosis of biomass and the polymorphism of the 10 isozymes
as well as 29 RFLP markers. However, the correlation coefficients were
not so high. It seemed to be difficult to use the polymorphism of mar
kers as an index of heterosis. The analysis of each marker and heteros
is showed that several markers which were located dispersedly over the
chromosomes showed significant correlations with the heterosis of bio
mass. According to the diallel analysis, more than 10 genes were relat
ed to the heterosis of biomass. Hybrids between indica varieties which
have biomass controlled by dominant genes and japonica varieties whic
h show over-dominance in crosses with indica are promising for breedin
g hybrid varieties with high biomass coupled with high yielding.